The present invention relates to fluid nozzles and, in particular, to hydraulic jet drilling wherein high-speed streams of fluid are emitted from nozzles on the drill bit.
In a typical rotary drilling operation, a rotary drill bit is rotated while being advanced into a soil or rock formation. The soil or rock is cut by cutting elements on the drill bit, and these cuttings are flushed from the borehole by the circulation of drilling fluid toward the top of the hole. The drilling fluid is delivered to the drill bit downwardly through a passage in the drill stem and is ejected outwardly through nozzles disposed in the face of the drill bit face. The ejected drilling fluid is directed outwardly through the nozzles at high speed (e.g., at 100 feet/sec.) to aid in cutting of the rock and cooling of the drill bit.
Conventional nozzles are described in Goodwin U.S. Pat. No. 3,120,284 issued Feb. 4, 1964; Payne U.S. Pat. No. 2,855,182 issued Oct. 7, 1958; Swart U.S. Pat. No. 2,950,090, issued Aug. 23, 1960; and Radtke U.S. Pat. No. 4,381,824, issued May 3, 1983.
In the Radtke patent, a nozzle is removably secured within a bore in the drill bit. The nozzles are proximate to the bottom of the borehole and are subjected to the action of abrasive particles moving at high speeds in that region. Thus, the nozzles are eventually abraded to the point where they fall out or are replaced. Accordingly, the nozzles are attached in a readily replaceable manner, such as by means of a threaded connection between the nozzles and the bores 18 in which they are positioned. A threaded connection is effective in resisting premature dislodgement of the nozzle, aided by the resistance to turning which is imposed by a resilient O-ring seal. An outer flange of the nozzle overlies the threads and protects same since the flange is formed of a hard material such as tungsten carbide, whereas the threads are formed of steel.
The jet openings of the nozzle are typically circular and in alignment with the longitudinal axis of the nozzle. Thus, the orientation of the jet stream is dictated by the orientation of the bores in which the nozzles are mounted and cannot be altered once the nozzles have been installed.
It is an object of the present invention to provide nozzles on a rotary drill bit in which the orientation of the jet can be adjusted after the nozzle has been installed. Laboratory and field testing have indicated improved drilling rates with vortex or elongated nozzles that are oriented properly with polycrystalline diamond bit cutting structures.
Another object is to provide such a nozzle in which the nozzles are threaded, and the threads are shielded against contact by abrasive particles in the borehole.
A further object is to provide such a nozzle in which the nozzles can be securely installed to avoid undue vibration.